Chapter 9
Lesson 9.1 Intro to Respiration
*Organisms get the energy they need from food. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. The Calorie (capitol C) that is used on food labels is a kilocalorie, or 1000 calories.
Cells can use all sorts of molecules for food, including fats, proteins, and carbohydrates.
1 gram of carb = 4 Calories
1 gram of protein = 4 Calories
1 gram of fat (lipid) = 9 Calories
But, unlike this burning marshmallow, cells don't release all the stored energy in food at once.
Cellular respiration is the process that releases energy from food in the presence of oxygen.
The chemical equation that represents cellular respiration is
6O2 + C6H12O6 -------> 6CO2 + 6H2O + Energy
or
Oxygen + Glucose ---------> Carbon Dioxide + Water + Energy
If cellular respiration took place in one step, however, all of the energy from glucose would be released at once, and most of it would be lost in the form of light and heat.
STAGES OF CELLULAR RESPIRATION
Cellular respiration captures the energy from food in three main stages
Glycolysis - the splitting of glucose (extracts only 10% of energy in glucose) into 2 pyruvic acids
Krebs Cycle - a series of energy extracting reactions that breaks down pyruvic acid into CO2
Electron Transport Chain - uses all the energy captured in first two processes to generate ATP
Aerobic - requires Oxygen
Anaerobic - does not require Oxygen
Gycolysis - anaerobic, occurs in cytoplasm
Krebs Cycle - aerobic, occurs in mitochondria
ETC - aerobic, occurs in mitochondria
The products of Glycolysis, 2 Pyruvic Acids, can now move into the mitochondria and go through the 2nd process of respiration, the Krebs Cycle.
THE KREBS CYCLE
In the Krebs Cycle, which occurs in the matrix of the mitochondria, Pyruvic Acid is broken down to CO2 in a series of energy-extracting reactions.
These include:
Pyruvic Acid
to
Acetic Acid + C(exhaled as CO2)
to
Acetic Acid is attached to CoenzymeA
becoming
Acetyl-CoA
which bonds with a 4-Carbon cyclic molecule forming
Citric Acid
Citric Acid is broken to
a 5-Carbon molecule + CO2
then
a 4-Carbon molecule + CO2
**Each time bonds are broken, "Energy police" NAD+ and FAD swoop in and collect the high energy electrons lost and carry them away to the ETC!
In addition, 1 ATP comes from each turn of the Krebs Cycle. Each glucose molecule spins 2 Krebs cycles from it's 2 molecules of Pyruvic Acid. So, Krebs spits out 2 ATPS from each glucose!
As a result of Kreb's Cycle, each Pyruvic Acid (3 Carbons) is broken down releasing 3 CO2s into the air while the energy from these bonds was collected and sent to the ATP Factory, the Electron Transport Chain (ETC).
THE KREBS CYCLE
Similar to the ETC in photosynthesis, the ETC in respiration uses high energy electrons from glycolysis and the Krebs cycle to convert ADP into ATP.
The "energy police" (high energy electron carriers) NAD+ and FAD carry electrons loaded with energy to the ETC.
NAD+ + 2e- + H+ -------> NADH
and
FAD + 2e- + 2H+ --------> FADH2
The ETC occurs in the inner membrane of the mitochondria where transport proteins are embedded. NADH and FADH2 drop off their high energy electrons in the membrane where they move from protein to protein passing on their energy to them. The job of the transport proteins is to pump H+ ions across the membrane against their concentration gradient from low to high concentration (active transport). This causes an extreme concentration gradient with the high being in the Intermembrane Space (between the two membranes) and the low being in the matrix. As are the laws of nature, H+ will gladly diffuse (passive transport) from high to low concentration and does this through the good sport enzyme protein, ATP Synthase. When H+ ions fly through ATP Synthase trying to escape the crowd, this causes ATP Synthase to spin, and this energy is used to add P (phosphates) to ADP making ATPs.
As it turns out, after the electrons have given away all their energy, they are accepted by Oxygen, which joins with the Hydrogens dropped off by NADH and FADH2 forming Water molecules (H2O) which are exhaled with the CO2 released during the Krebs Cycle.
Powerpoint 9.2 click here:
https://docs.google.com/presentation/d/1TSmwY6QK2q2hXsVynW7x9VwJK29SQvoyeBMKiwlJdNU/edit?usp=sharing
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Lesson 9.3 Fermentation
What if Oxygen is not around?
What happens when you hold your breath and dive under water, or use up oxygen more quickly than you can replace it?
Recall that glycolysis is an anaerobic process which can produce ATP quickly. But, when a cell generates large amts of AP from glycolysis, it runs into a problem.
In just a few seconds, all of the cell's available NAD+ molecules used to collect high energy electrons from Glycolysis will get used up if the ETC does not occur (an aerobic process). This will leave the cell with no available NAD+ an therefore, will shut down Glycolysis and production of ATPs.
In the absence of O2, fermentation, which takes place in the cytoplasm, releases energy from food molecules producing ATP!
During fermentation, cells convert NADH to NAD+ by passing high energy electrons back to Pyruvic Acid. This action concerts NADH back into the electron carrier NAD+, allowing glycolysis to produce a steady supply of ATP.
Fermentation can take two pathways:
Alcoholic Fermentation
and
Lactic Acid Fermentation
In Alcoholic Fermentation, which is carried out by yeasts and a few other microorganisms, the Pyruvic Acid accepts the high energy electrons from glycolysis and is broken down to ethyl alcohol and carbon dioxide while relieving NADH of it's electrons so that it becomes NAD+ again and recycles back through glycolysis, keeping it going.
https://docs.google.com/presentation/d/1rTcDKXVzqWIfEekpY4aPSDq63YYDmtk-hXoh70Q1m8s/edit?usp=sharing
*Organisms get the energy they need from food. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. The Calorie (capitol C) that is used on food labels is a kilocalorie, or 1000 calories.
Cells can use all sorts of molecules for food, including fats, proteins, and carbohydrates.
1 gram of carb = 4 Calories
1 gram of protein = 4 Calories
1 gram of fat (lipid) = 9 Calories
But, unlike this burning marshmallow, cells don't release all the stored energy in food at once.
Cellular respiration is the process that releases energy from food in the presence of oxygen.
The chemical equation that represents cellular respiration is
6O2 + C6H12O6 -------> 6CO2 + 6H2O + Energy
or
Oxygen + Glucose ---------> Carbon Dioxide + Water + Energy
If cellular respiration took place in one step, however, all of the energy from glucose would be released at once, and most of it would be lost in the form of light and heat.
STAGES OF CELLULAR RESPIRATION
Glycolysis - the splitting of glucose (extracts only 10% of energy in glucose) into 2 pyruvic acids
Krebs Cycle - a series of energy extracting reactions that breaks down pyruvic acid into CO2
Electron Transport Chain - uses all the energy captured in first two processes to generate ATP
Aerobic - requires Oxygen
Anaerobic - does not require Oxygen
Gycolysis - anaerobic, occurs in cytoplasm
Krebs Cycle - aerobic, occurs in mitochondria
ETC - aerobic, occurs in mitochondria
 |
| Photosynthesis removes carbon dioxide from the atmosphere, and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere, and cellular respiration uses that oxygen to release energy from food. Photosynthesis and Cellular Respiration are opposite processes. For 9.1 Powerpoint click here https://docs.google.com/presentation/d/1VUHSuLo03bNmLdFQS0ZRnkPC_AeT17i5gRosOKaJJLY/edit?usp=sharing ------------------------------------------------------------------------------------------------------------------------------- Lesson 9.2 The Process of Cellular Respiration Food Burns!  Flour is so flammable that it has caused several explosions, including the one seen here at London's City Flour Mills in 1872. More recently, a sugar factory exploded along the Savannah river. Glycolysis **The benefits of glycolysis are that it happens very fast and does not require oxygen!** To initiate glycolysis, an investment of 2 ATP (activation energy) must be made. During Glycolysis, 1 molecule of glucose, a 6-carbon compound, is transformed into 2 molecules of Pyruvic Acid, a 3-carbon compound. Energy is released in the form of high energy electrons when the bonds are broken and is captured by the "energy police" NAD+ and carried away to the ETC. In addition, 4 ATPs come from Glycolysis with a net yield of +2ATP |
The products of Glycolysis, 2 Pyruvic Acids, can now move into the mitochondria and go through the 2nd process of respiration, the Krebs Cycle.
THE KREBS CYCLE
In the Krebs Cycle, which occurs in the matrix of the mitochondria, Pyruvic Acid is broken down to CO2 in a series of energy-extracting reactions.
These include:
Pyruvic Acid
to
Acetic Acid + C(exhaled as CO2)
to
Acetic Acid is attached to CoenzymeA
becoming
Acetyl-CoA
which bonds with a 4-Carbon cyclic molecule forming
Citric Acid
Citric Acid is broken to
a 5-Carbon molecule + CO2
then
a 4-Carbon molecule + CO2
**Each time bonds are broken, "Energy police" NAD+ and FAD swoop in and collect the high energy electrons lost and carry them away to the ETC!
In addition, 1 ATP comes from each turn of the Krebs Cycle. Each glucose molecule spins 2 Krebs cycles from it's 2 molecules of Pyruvic Acid. So, Krebs spits out 2 ATPS from each glucose!
As a result of Kreb's Cycle, each Pyruvic Acid (3 Carbons) is broken down releasing 3 CO2s into the air while the energy from these bonds was collected and sent to the ATP Factory, the Electron Transport Chain (ETC).
THE KREBS CYCLE
Similar to the ETC in photosynthesis, the ETC in respiration uses high energy electrons from glycolysis and the Krebs cycle to convert ADP into ATP.
The "energy police" (high energy electron carriers) NAD+ and FAD carry electrons loaded with energy to the ETC.
NAD+ + 2e- + H+ -------> NADH
and
FAD + 2e- + 2H+ --------> FADH2
The ETC occurs in the inner membrane of the mitochondria where transport proteins are embedded. NADH and FADH2 drop off their high energy electrons in the membrane where they move from protein to protein passing on their energy to them. The job of the transport proteins is to pump H+ ions across the membrane against their concentration gradient from low to high concentration (active transport). This causes an extreme concentration gradient with the high being in the Intermembrane Space (between the two membranes) and the low being in the matrix. As are the laws of nature, H+ will gladly diffuse (passive transport) from high to low concentration and does this through the good sport enzyme protein, ATP Synthase. When H+ ions fly through ATP Synthase trying to escape the crowd, this causes ATP Synthase to spin, and this energy is used to add P (phosphates) to ADP making ATPs.
The ETC is an ATP Machine and spits out 32 ATPS for every Glucose molecule.
Together, Glycolysis, the Krebs cycle, and the ETC release about 36 molecules of ATP per molecule of Glucose!
Under aerobic conditions these pathways enable the cell to produce 18 times as much energy as can be generated by anaerobic glycolysis alone.
Our diets contain much more than glucose, of course, but that's no problem for the cell.
Complex carbs are broken down to simple sugars like glucose. Lipids and proteins can be broken down into molecules that enter the Krebs cycle or glycolysis at one of several places.
36%
The 36 ATP molecules generated during respiration of one glucose represent only 36% of the total energy of glucose. What happens to the remaining 64%? It is released as heat, which is what keeps our bodies warm!
Powerpoint 9.2 click here:
https://docs.google.com/presentation/d/1TSmwY6QK2q2hXsVynW7x9VwJK29SQvoyeBMKiwlJdNU/edit?usp=sharing
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Lesson 9.3 Fermentation
What if Oxygen is not around?
What happens when you hold your breath and dive under water, or use up oxygen more quickly than you can replace it?
Recall that glycolysis is an anaerobic process which can produce ATP quickly. But, when a cell generates large amts of AP from glycolysis, it runs into a problem.
In just a few seconds, all of the cell's available NAD+ molecules used to collect high energy electrons from Glycolysis will get used up if the ETC does not occur (an aerobic process). This will leave the cell with no available NAD+ an therefore, will shut down Glycolysis and production of ATPs.
In the absence of O2, fermentation, which takes place in the cytoplasm, releases energy from food molecules producing ATP!
During fermentation, cells convert NADH to NAD+ by passing high energy electrons back to Pyruvic Acid. This action concerts NADH back into the electron carrier NAD+, allowing glycolysis to produce a steady supply of ATP.
Fermentation can take two pathways:
Alcoholic Fermentation
and
Lactic Acid Fermentation
In Alcoholic Fermentation, which is carried out by yeasts and a few other microorganisms, the Pyruvic Acid accepts the high energy electrons from glycolysis and is broken down to ethyl alcohol and carbon dioxide while relieving NADH of it's electrons so that it becomes NAD+ again and recycles back through glycolysis, keeping it going.
In industry, yeast are used to make breads and alcohols
In Lactic Acid Fermentation, which is carried out by most other organisms, Pyruvic Acid accepts the high energy electrons from glycolysis and is converted to Lactic Acid, another 3 Carbon molecule, releasing the high energy electrons from NADH so that it becomes NAD+ again and recycles back through glycolysis, keeping it going.
During extreme exercise or lack of O2, Lactic Acid will build up in the cells building an "Oxygen Debt" which has to be paid back by heavy breathing in humans.
Lactic Acid Fermentation is used in industry to make several different foods including sour cream, yogurt, sauerkraut, buttermilk, pickles and cheese
Where does our body get the energy it needs for quick energy?
For short, quick bursts of energy, the body uses ATP already in muscles as well as ATP made by lactic acid fermentation. For exercise longer than about 90 seconds, cellular respiration is the only way to continue generating a supply of ATP.
1. 4-6 seconds worth from ATP already stored in the cells
2. About 90 seconds worth from Fermentation
3. From Cellular Respiration
After using Fermentation, heavy breathing must happen to "pay back" the Oxygen debt owed by using Fermentation. Cellular Respiration releases energy more slowly than Fermentation which is why even well-conditioned athletes have to pace themselves during a long race.
Glycogen
Your body stores energy in muscle and other tissues in the form of glycogen. Glycogen is broken down to glucose. These stores are usually only enough to last for 15-20 minutes of activity. After that, your body begins to break down other stored molecules, including fats, for energy.
Bears rely on the stores of fat to be broken down for energy while they are hibernating.
Powerpoint 9.3 click here:
https://docs.google.com/presentation/d/1rTcDKXVzqWIfEekpY4aPSDq63YYDmtk-hXoh70Q1m8s/edit?usp=sharing
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